Antistatic layer for photographic materials

ABSTRACT

CERTAIN POLYGLYCOL DERIVATIVES ARE VERY EFFECTIVE ANTISTATIC AGENTS FOR PHOTOGRAPHIC FILMS CARRYING GELATIN LAYERS. THESE AGENTS ARE OF THE FORMULA:   R1(-X-CO-((O-CH2-CH2)N2-O-CH(-CH3)-CH2)M-(O-CH2-CH2)N1-   O-R)Y   WHEREIN:   R IS AN ALKYL HAVING 6-18 CARBON ATOMS, A PHENYL GROUP INCLUDING A SUBSTITUTED PHENYL GROUP; X IS 0 OR AN IMINO GROUP; R1 IS A Y-VALENT ORGANIC GROUP OF THE PHENYL OR NAPHTHYL SERIES; N1 OR N2 IS AN INTEGER FROM 4 TO 8; M IS 0 OR 1 AND Y IS 1, 2, OR 3.

United States Patent US. Cl. 96-87 2 Claims ABSTRACT OF THE DISCLOSURE Certain polyglycol derivatives are very effective antistatic agents for photographic films carrying gelatin layers. These agents are of the formula:

wherein:

R is an alkyl having- 6l8 carbon atoms, a phenyl group including a substituted phenyl group;

X is 0 or an imino group;

R is a y-valent organic group of the phenyl or naphthyl series;

n or n is an integer from 4 to 8;

m is 0 or 1 and y is 1, 2, or 3.

Great ditficulties arise both in the production and in the use of photographic films owing to accumulation of electric charge. These static electric charges may be caused by friction between the film and the rollers or other parts of the apparatus through which the film runs, where contact is made with rough surfaces or as a result of numerous other factors. Static discharges occurring in the film before development are recognizable after the film has been worked up by the presence of irregular stripes or lines, or dark points, which are caused by the spark exposure of the emulsion at these positions. The presence of static charge in the processed film is also undesirable, especially in the case of cinematographic film, since it increases the friction of the film as it runs through the projector.

Electrostatic charging of the film surface can be reduced by adding matting agents to the protective layers to diminish the adhesion between two surfaces of the photographic material which are in contact with each other. The formation of electrostatic charges can also be avoided by the addition of electrically conductive materials to an outermost layer.

Many of these additives which have a satisfactory antistatic action, are of limited utility since they deleteriously effect the photographic properties.

Thus, quaternary salts cannot be used in photographic materials because they cause fogging. Hygroscopic materials such as glycerol, potassium acetate or lithium chloride cause the layers to adhere to each other and are ineffective at low humidities. High molecular carboxylic or sulfonic acids such as sodium salts of polystyrene sulfonic acid and polyvinylsulfonic acid have agood antistatic effect when applied direct to a hydrophobic layer support, but this effect is greatly reduced when used in gelatin or emulsion layers. Chromium complexes react with gelatin and therefore can only be used under certain conditions.

3,552,972 Patented Jan. 5, 1971 ice It is among the objects of the present invention to provide antistatic agents that are photographically inert and that can be used as additives to photographic protective layers.

We now have found that photographically inert -urethanes or esters of hydroxyalkylated fatty alcohols or hydroxyalkylated alkylphenols that are sparingly soluble in water are excellently suitable as antistatic additives for photographic layers preferably gelatin layers. The compounds of the invention are characterized by the following formula:

wherein:

R=alkyl having preferably 6-18 carbon atoms, aryl, preferably phenyl, aralkyl such as benzyl or phenylethyl or cycloalkyl such as cyclohexyl; the above substituents, especially the phenyl groups, may be further substituted in any way desired;

X=a simple chemical bond or a bivalent imino group;

R is a y-valent organic group of the kind defined under R;

n, and 11 are integers from 4 to 8 inclusive;

m=0 or 1; and

y=1, 2 or 3.

These copolymers (in the case where m=1) are block polymers and not compounds which contain ethylene oxide and propylene oxide in statistical distribution.

The compounds to be used in accordance with the invention are generally highly viscous, syrupy substances. When used for photographic purposes, they are dissolved in a photographically inert solvent, preferably a low molecular weight aliphatic alcohol, and this solution is emulsified into the casting solution of the protective layer. In the final layer the antistatic agents are substantially heterogeneously distributed in the layer in the form of fine particles.

The compounds according to the invention are employed in quantities of 0.03 to 0.20 g., preferably 0.05 to 0.075 per g. of the binding agent. They may be used alone or in combination with surface active substances such as anionic or non-ionic wetting agents or in combination with anti-Newton additives such as polystyrene, polymethacrylic acid esters or urea formaldehyde polymers. The last mentioned additives are also present in the final layer in the form of heterogeneously distributed particles having a size of 1-3 microns. Smooth layers that have an excellent antistatic effect are thereby obtained.

As binding agents for the antistatic layer there can be used the hydrophilic and water-permeable film-forming compounds customarily employed for photographic layers, for example proteins preferably gelatin, cellulose derivatives such as alkyl cellulose for instance hydroxyethyl cellulose or carboxyl methyl cellulose, alginic acid and derivatives thereof, polyvinyl alcohols, polyvinyl pyrrolidone and the like.

The compounds to be used according to the invention can be used in light-sensitive silver halide emulsion layers, antihalation layers and NC-layers for black-white or color-photographic films. They do not cause fogging, do not accelerate development, do not migrate from the layers or cause sticking of the layers.

The antistatic agents are sparingly soluble in water and are photographically inert. When m=0 (see general formula) they have preferably at the most a total of 8 ethylene oxide units. When the groups R are strongly hydrophobic, the compounds contain preferably more than 8 ethylene oxide units so that they are more readily capable of being emulsified.

Suitable compounds include those of the following formulae:

A I A (VII) (VIII) The compounds to be used according to the invention are prepared by known methods. The preparation of compounds 1 and 7 is described in detail below. The other compounds are prepared in a similar manner.

COMPOUND l moved in a rotary evaporator. The oily, yellow brown product is again filtered at to C.

52.0 g. of hydroxyalkylated octadecanol (as described above) are dissolved in 150 ml. of absolute toluene, and the solution is mixed with a solution of 6.0 g. of phenylisooyanate in ml. of absolute toluene and stirred for 5 hours at C. The reaction mixture is then boiled with 1 ml. of methanol for 5 minutes. After briefly boiling with active charcoal, removing the charcoal by filtration under suction and removing the solvent, a pale brown product is obtained which has a honeylike consistency.

COMPOUND VII A solution of 9.9 g. of 3,5-dinitrobenzoyl chloride in ml. of benzene is added dropwise to a mixture of 42 g. of n-dodecylphenol which has been hydroxyalkylated in a manner analogous to Compound 1, 20 ml. of benzene and 5 g. of pyridine, and the reaction mixture is stirred at room temperature for 5 hours and at 50 C. for one hour. After cooling, the reaction mixture is poured on ice, acidified with 2 N H 50 treated with saturated sodium chloride solution, and extracted several times with methylene dichloride. The combined extracts are freed from solvent after drying over K in a vacuum.

EXAMPLE 1 Samples of a silver iodobromide gelatin emulsion layer on cellulose acetate support are overcoated with protective layers about 1.1 to 1.3 in thickness which contain different antistatic agents. The casting solution for the protective coatings have the following composition:

1 kg. of gelatin 50 l. of water 3.75 l. of 2% aqueous mucochloric acid as hardener 0.5 l. of 7.5% saponin 0.9 l. of 10% methanolic solution of an antistatic agent.

The 10% methanolic solution of the antistatic agent is emulsified into the casting composition at temperatures between 30 and 40 C. with stirring. The pH of the casting solution which is to form the protective coating is adjusted to 6.5 with sodium hydroxide solution.

The protective coating is applied by usual methods after the emulsion layer has solidified or simultaneously with the application of the emulsion layer -by the vacuum air brush process.

The antistatic effect is tested after air conditioning the sample strips for 2 days, the electrostatic charging in volts per cm. (v./cm.) is determined by means of the rotating field strength measuring instrument according to Schwenkhagen. The intensity of charge was measured at 60% relative humidity.

v./cm.(60% humidity) 45 ml. of a 10% methanolic solution of one of the above mentioned antistatic materials is incorporated by emulsification as described in Example 1 into a gelatin solution of the following composition:

1000 ml. of water 110 g. of gelatin 60 ml. of a 10% aqueous solution of fuchsin 18 ml. of a aqueous solution of chrome alum 4 ml. of a 5% aqueous solution of saponin and 30 ml. of ethyl alcohol.

The casting solution is applied onto the rear side of a transparent support of cellulose acetate and dried. The layer serves as a non-curling layer. The other side of the support is coated with a silver halide gelatin emulsion layer.

The antistatic test of the resulting layer are preformed as in Example 1:

v./cm. (60% humidity) Standard (without additive) 1200 Compound III 130 Compound IV 140 Compound VI 180 EXAMPLE 3 15 ml. of a solution of one of the above mentioned antistatic agents is incorporated by emulsification as described in Example 1 into a gelatin solution having the following composition:

1000 ml. of water 30 g. of gelatin 7.5 ml. of a 5% aqueous solution of triacrylic formal 15 ml. of a 5% aqueous solution of saponin.

This solution is applied as protective layer onto the light-sensitive silver halide gelatin emulsion layers of a multi-layered color photographic material and dried.

Antistatic tests of the final layers are performed as described in Example 1:

v. cm. (60% humidity) Standard (without additive) Compound III 15 Compound IV 24 Compound VI 12 EXAMPLE 4 A photographic material comprising a silver iodobromide gelatin emulsion layer and an uppermost protective layer which does not contain an antistatic agent is treated with 0.01 to 0.25% solutions of the antistatic agents mentioned hereinafter (a) in water or (b) in methylene dichloride.

The electrostatic charge of the air conditioned samples is measured at 60% humidity. Comparison measurements are carried out on samples of photographic material which have been treated only with water or methylene dichloride but have otherwise the same composition.

Antistatic tests of the samples (a) application of antistatic agent from aqueous solution:

dichloride solution:

v./cm. (60% humidity) Without antistatic agent 20 Compound V 0.5

Compound X 2 EXAMPLE 5 The following example illustrates the possibility of combining the antistatic agents according'to the invention with known antistatic agents. [Representatives of two groups of antistatic agents are used, namely:

(a) polystyrene sulfonic acid as representative of high molecular weight compounds which contain carboxyl or sulfone groups, and

(b) various alkali metal salts (with the exception of NaCl) which do not coagulate gelatin.

The antistatic agents are incorporated into a protective gelatin layer which is applied onto a silver iodobromide gelatin emulsion layer according to Example 1. This layer contains, either alone or in combination, as will be seen from the following tables, based on the dry weight of gelatin, 20% by weight of polystyrene sulfonic acid (PSS), 6% by weight of alkali metal salt or 6% by weight of the antistatic agent according to the invention.

After application of the protective layer, the samples are dried, and the antistatic properties are tested after 2 days air conditioning (60% relative humidity as described in Example 1). The results are shown in the following table:

Electro- Surface static resischarge tivity Inventive Additives in in 10 compounds PSS Salts volt/em. ohm

Gelatin 150 8.1 15 2. 1 0. 5 O. Plus KNOa 0.5 0.7 Compound III Plus NagSO4 0.5 0. U 9 1. 5 Plus KNOz 3 1.2 P1115 19212304"... 4 1.2 3 1. 6 Plus KNO3 1 1.4 Compound r .ii ililffi iiii: 1. 13% Plus KN O 1 0. 9 Plus N 31250 1 1. 2 0. 2 2. 2 1 i i l? us at 4 O. Compound VI 1 2 Plus KNO 2.5 1.5 P1118 Na2SO4. 1 1. 5

1 Layer without antistatic additives.

The surface resistivity is determined with a measuring instrument which has two comb electrodes cm. in length arranged parallel to each other at a distance of 2 cm., and the samples which have been adequately air conditioned, are pressed at a constant pressure against these electrodes. The resistivity is registered with a teraohmmeter connected to the instrument.

What is claimed is:

' 1. In an electrically non-conductive support carrying a photographic gelatin emulsion layer and an ellective amount of an antistatic agent, the improvement according to which such agent has the formula:

References Cited UNITED STATES PATENTS 2,725,297 11/1955 Morey 9687 3,210,191 10/1965 Willems et al. 96107 3,234,170 2/1966 Stumpf et a1. 260613 3,294,540 12/1966 Goife 96107 3,428,456 2/1969 Grabhoefer 9687 FOREIGN PATENTS 687,558 9/1951 Great Britain 9687 WILLIAM D. MARTIN, Primary Examiner M. SOFOCELEOUS, Assistant Examiner US. Cl. XJR. 

